import React, { createContext, useReducer } from 'react';
//传一个空对象默认值
export const ColorContext = createContext({})
export const UPDATE_COLOR = 'UPDATE_COLOR';
const reducer= (state,action)=>{
    switch(action.type){
        case UPDATE_COLOR:
            return action.color
        default:
            return state
    }
}
export const Color = props=>{
    const [color,dispatch]=useReducer(reducer,'blue');
    return (
        <ColorContext.Provider value={{color,dispatch}}>
            {props.children}
        </ColorContext.Provider>
    )
}